The present invention relates to an electrical connector for connecting or disconnecting a conductive pin to or from a contact by moving a connector part together with the conductive pin in a direction perpendicular to an axis of the contact and, in particular, to such an electrical connector having a preload member for preloading or biasing the contact prior to connection between the conductive pin and the contact so as to achieve a so-called zero-insertion force.
In a known electrical connector for electrically connecting or disconnecting a number of terminal pins of an LSI (large scale integrated) circuit to or from a circuit board, a base insulator having a plurality of contacts are mounted onto the circuit board. A cover insulator is assembled onto the base insulator to be relatively movable in a moving direction normal to the axis of each contact. The cover insulator has a plurality of holes for passing the terminal pins of the LSI circuit therethrough and also has a plurality of preload pins each of which is disposed adjacent to each of the holes in the moving direction. The preload pins are similar in dimension to the terminal pins. When the cover insulator is located at a first position, the preload pins are in contact with the contacts to preload or bias the contacts, respectively, in a biasing direction normal to the moving direction. When the cover insulator is moved in the moving direction together with the LSI circuit with the terminal pins inserted in the holes in the cover insulator, the terminal pins are brought into contact with the contacts of the connector in place of the preload pins. That is, since the contacts are preloaded or biased in the biasing direction before the terminal pins come into contact with the contacts so as to readily accept the terminal pins, a reduced force is only required for moving the cover insulator in the moving direction to bring the terminal pins into contact with the contacts.
The connector of this type will herein be referred to as a preload-type connector.
The preload-type connector described above is disclosed in JPY 2-16542 (Jikkohei 2-16542) and JPU 60-162391 (Jikkaisho 60-162391).
U.S. Pat. No. 5,044,973 corresponding to JPA 2-192679 (Tokkaihei 2-192679) discloses another preload-type connector which is improved in that the preload pins are fixed to a slider insulator which is movable in the moving direction but independently from the cover insulator. The slider insulator has a plurality of elongated holes for passing the terminal pins therethrough. The elongated holes are greater than the holes of the cover insulator in the moving direction. The slider insulator is moved beforehand to preload the contacts by the preload pins. Then, the cover insulator is moved together with the LSI circuit to bring the terminal pins to positions of the contacts. Thereafter, the slider insulator is further moved to free the contacts from the preloaded condition. Thus, the contacts come into contact with the terminal pins.
In the known preload-type connectors, the preload pins are attached or fixed to the cover insulator or the slider insulator. The fixing process is very complicated because it is difficult to fix the preload pins to the insulator at desired positions with a high accuracy and a precise orientation. Furthermore, the preload pins may be deformed during the fixing process.
On the other hand, contacting portions of the contacts engage or come into contact not only with the terminal pins but also with the preload pins. Therefore, the contacting portions are readily worn and contaminated so that the reliability of the contacts is lowered and the lifetime of the contacts becomes short.